Mechanical floor cleaners or floor polishers typically possess a circular pad driven to rotate about a vertical axis by an electric motor mounted on a frame or housing located above the pad, and an upwardly angled operating handle extending from the frame or housing generally upwards to a suitable height for use.
Such cleaners or polishers can be readily caused to move to or fro transversely by the operator. This is done by lifting or lowering the handle, so as to tilt the pad and cause either the front half or the rear half of the pad to engage relatively more strongly with the floor and thus give the pad a useful sideways component of motion. By judicious tilting motion of the handle the operator can move slowly forwards or backwards and effectively clean or polish a wide track of the floor to either side of his personal movement.
Historically, there have been problems in providing a single machine for both cleaning and polishing purposes. It is not difficult to design suitable pads and adapt them for selective interchange, but the weight of the original machines was such that while the optimum speed of the motor, or a suitable ratio could be used for polishing, the more robust action of cleaning would generate enough friction to stall the motor or to give undesirable wear, noise, and heat problems.
European Patent 0122181 shows an earlier solution to this problem. In this patent, the weight of the equipment is largely carried by the two rear castor wheels, but the weight of the pad and motor is generally supported on a separate sub-frame tiltable about a transverse axis in relation to the remainder of the equipment by virtue of a linkage adjustably attached to a suitable part of the handle. Thus, when the handle is raised or lowered the sub-frame is tilted accordingly and the pad is tilted so that the equipment moves transversely as required. Because the total weight is split between the castors and the pad, high speeds suitable for dry scrubbing/polishing can also be used (with a changed pad) for cleaning purposes.
Although such equipment is valuable for the purpose stated, provision of a mechanical linkage adds to cost and complexity, as does the need to adjust the link connection for each different user so as to give a comfortable working height. Moreover, the link movement has regions of insensitivity, giving a less controlled or lunging sideways movement, especially when wear has taken place at the joints. The handle, wherever adjusted for use, droops downward under its own weight when not in use, and has therefore to be positively held up at the preferred height by the user.
A more recent proposal is to attach the handle directly to the motor housing and then to mount this housing on a axis tiltable in smoothly operating bearings, one to each side, journalled to the main frame of the machine. The main portion of the machine is supported on the two rear castors and one forward, height-adjustable, castor.
Raising or lowering the handle again gives the necessary tilt to the pad to promote side to side cleaning or polishing movement.
The handle in this known device is supported against falling downwards by compression springs providing support for the motor housing, such springs being located one to each side behind the smoothly operating bearings and forward of the point of attachment of the handle.
While this device is simpler in construction than the earlier device described in European Patent 0122181, it still has the disadvantage that the compression springs will allow the handle to droop beneath any given adjusted user optimum position, that is to say a position where for a given user the pad is horizontal. Also, the upward movement, leading to forward tilt of the pad, appears to act only against gravity so that there are two different types of forces to overcome depending upon whether the handle is raised or lowered. This again leads to a tendency to lunging or swooping movement in sideways travel.